<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style>
			div{width: 200px;height: 200px;}
			#div1{background: red;}
			#div2{
				background: black;
				animation: dh1 3s linear 1s infinite alternate;
			}
			
			/* 定义一个动画 */
			@keyframes dh1{
				10%{width: 300px;}
				20%{width: 400px;}
				50%{width: 700px;}
				100%{width: 1500px;}
			}
		</style>
	</head>
	<body>
		<div id="div1"></div>
		<div id="div2"></div>
	</body>
</html>
